CHEMISTRY COMMUNITY

Rosha Mamita 2H

catalysts lower the activation energy of reactions and speed them up. and an enzyme is an example of one of them

Rosha Mamita 2H

an enzyme acts as a catalyst in reactions.

Rosha Mamita 2H

if there is no change in volume, no work is done. If there is no change in pressure, you would use one of the given formulas

Rosha Mamita 2H

then there is no work if there is no change in volume

Rosha Mamita 2H

half life refers to the time it takes for a substance to decay by one-half of its initial amount. Half life and its equation are used to determine how old a substance is, the initial amount of a substance, or the final amount of a substance after a period of time

Rosha Mamita 2H

The final definitely will be cumulative. The format will most likely be that there is a question with many parts for each topic we discussed, ex a question on kinetics, a question on electrochem, a question on thermodynamics

Rosha Mamita 2H

The rate determining step will be the slowest step in the reaction, and that determines the rate law of the overall reaction

Rosha Mamita 2H

unimolecular refers to one species, bimolecular refers to two species, and termolecular refers to three species

Rosha Mamita 2H

The molecularity refers to the number of species in an elementary step, you can think of it as having to do with the number of reactants in the reaction

Rosha Mamita 2H

n represents the number of electrons transferred in the process

Rosha Mamita 2H

If a certain reaction is involved, the answer should be in units of kJ/mol

Rosha Mamita 2H

The problem would specify if the reaction was happening in an acidic or basic environment

Rosha Mamita 2H

The problem would specify if the reaction was happening in an acidic or basic environment

Rosha Mamita 2H

It most likely has to do with the coefficient in front of the substance used in the equation

Rosha Mamita 2H

This is what he said on his website: "Test 2 covers all topics on Gibbs free energy and electrochemistry up to but not including the Nernst equation (which is all the new material covered in class Weeks 6 and 7). Test 2 starts Tuesday of Week 8.", I believe its only electrochemistry and Gi...

Rosha Mamita 2H

Isothermal means that a system stays at a constant temperature

Rosha Mamita 2H

Though I wouldn't know whether or not we would be doing it on a midterm/final, you can rearrange equations, such as q=mc(T change), to find the specific heat capacity of a molecule if need be

Rosha Mamita 2H

Usually in equations, S refers to entropy and H refers to enthalpy, you can use that to apply what's given/asked for in the problem and the equations on the equation sheets

Rosha Mamita 2H

However if talking about the temperature itself, Kelvin and Celsius need to be converted from one temperature unit to another depending on what units the equations requires

Rosha Mamita 2H

When talking about a change in temperature, the change in values of Kelvin and Celsius are interchangeable since a one degree difference in Kelvin is the same as a one degree difference in Celsius.

Rosha Mamita 2H

There are many conceptual factors to determining if gases are ideal or not, but for the sake of this course I think we are supposed to see every gas as an ideal gas. Many gases do not behave like ideal gases but we havent considered that in class yet

Rosha Mamita 2H

An ideal gas is a gas that would take up little to no volume in an area of high temperature and low pressure, and so if a gas behaves enough like an ideal gas, the ideal gas law is applicable

Rosha Mamita 2H

Gasses would have the highest entropy since a molecule can hold more positions in this state, then liquids would have the second highest entropy followed by solids

Rosha Mamita 2H

entropy can be thought of as the ways an object can be positioned in. more complex molecules have more microstate possibilities and therefore they would have a higher entropy.

Rosha Mamita 2H

It wont automatically favor a certain direction based on whether the equation is endothermic or exothermic, but increasing and decreasing the heat term will cause the reaction to favor a certain side. An endothermic reaction has the heat term on the left side and an exothermic reaction has the heat ...

Rosha Mamita 2H

Yes, your Kp expression would only be including the reactants and products in a gas phase and excluding all solids and liquids

Rosha Mamita 2H

I believe that water in a gas form would effect the resulting K value. However liquids and solids aren't included in K expressions and therefore have no effect on the K value

Rosha Mamita 2H

It wouldn't hurt to memorize some of the strong acids and bases, though you can tell if it is a weak or strong acid by looking at the K value

Rosha Mamita 2H

For those problems, you are usually given an initial molarity/partial pressure and are asked to find values relating to the equation being at equilibrium

Rosha Mamita 2H

Yes that is true, both reactions are occurring at equal rates at equilibrium

Rosha Mamita 2H

Because Kc and Kp could both be used for an equation with gas phase reactants and products

Rosha Mamita 2H

It all depends on whether the problem is asking you for an answer in terms of molarity or pressure, for example they may ask you for a Kc or Kp value in the problem

Rosha Mamita 2H

Amphoteric compounds have both basic and acidic character so they can act as either an acid or a base in a reaction, in comparison to a lot of molecules that are labeled as either an acid or base.

Rosha Mamita 2H

Ethan Breaux 1J wrote:Maybe I'm just reading this wrong but are you referring to see saw?

See saw refers to a molecule with formula AX4E (4 bonds and one lone pair) while T shaped refers to a molecule with formula AX3E2 (3 bonds and two lone pairs)

Rosha Mamita 2H

Only the bonds and lone pairs on the central atom determine the VSEPR shape of the molecule.

Rosha Mamita 2H

This is determined by the symmetry of the molecules and that symmetrical molecules would have dipole moments cancelling each other out. Though often, molecules with lone pairs tend to be polar because the pair’s dipole moment does not cancel out, however there are exceptions to this such as how squa...

Rosha Mamita 2H

The lewis structure of ClO2- would look like O=Cl-O, where the last O would have a negative charge

Rosha Mamita 2H

Bent and anglular are two different names for the same kind of VSEPR structure

Rosha Mamita 2H

Hydrogen bonding is the bond that hydrogen makes to highly electronegative F, O or N. These are more or less great dipole-dipole interactions so they are very polar

Rosha Mamita 2H

AX2E2 takes bond angles similar to those of tetrahedral, except the great repulsion of both lone pairs makes the bond angle less than 109.5. AX2E Two lone pairs creates more repulsion than one lone pair

Rosha Mamita 2H

This usually has to do with the lone pairs and how they create a grear repulsion, which makes bond angles slightly more different than the textbook value. In this case you would write that it is less than the normal bond angle

Rosha Mamita 2H

The atom that has the lowest ionization energy will be at the center, though there are exceptions. For example, hydrogen will never be a central atom

Rosha Mamita 2H

atoms with the lowest ionization energy tend to be the central atom, and in this case oxygen has the lowest ionization energy. Ionization energy decreases down a group and increases across a period.

Rosha Mamita 2H

For example, linear would be AX2E0, tetrahedral would be AX4E0, trigonal pyramidal would be AX3E1

Rosha Mamita 2H

The A refers to the central atom, the X refers to the number of bonded atoms, and the E refers to the number of lone pairs

Rosha Mamita 2H

Usually molecules with lone pairs tend to be polar, ex: trigonal pyramidal has 1 lone pair and is polar, unless the vsepr shape is non-symmetrical and in that case the bond would be non polar despite the lone pairs, ex: square planar has 2 lone pairs and is non-polar because it is symmetrical

Rosha Mamita 2H

f electronegativity values are given, the difference in electronegativity values is 0.4 or greater, the bond is polar.

Rosha Mamita 2H

This structure is called bent and the lone pair on the central atom repels the electrons away from the central atom, I'm not sure if we will go over this in class but we learned about this structure in high school and AP chemistry

Rosha Mamita 2H

Yes, though the shape will be different and would not be called linear

Rosha Mamita 2H

formal charges show the amount of electrons that are in the valence of an electron in an atom. If the formal charge is 0 then the atom is neutral and has the same amount of electrons as protons. A negative number shows that it has that many more electrons than it normally has and a positive number w...

Rosha Mamita 2H

I believe the formal charges will either be given/shown to us in some type of way, otherwise theres a chance he may have us memorize a select few transition metals' charges beforehand.

Rosha Mamita 2H

Each removal of a valence electron will take more energy than the last and be more difficult. This is due to a concept where it will take more energy to remove an electron from an atom that already has a positive charge because of a higher electrostatic force.

Rosha Mamita 2H

Down a group there is a greater distance between the nucleus and electrons of an atom because of added energy shells, so because sulphur's electrons are further away from its nucleus than oxygen, it will take less energy to remove an electron from sulphur. The farther an electron is from its nucleus...

Rosha Mamita 2H

The indeterminacy equation involves that delta p and delta t are equal to or greater than plancks constant over 4pi, so the maximum may even be infinite or to a value we cant calculate, but theres at least a minimum value that can be calculated if the equation has an equals sign.

Rosha Mamita 2H

We just need to know conceptually how this equation applies to working with orbitals

Rosha Mamita 2H

The conversion seems to be on the equation sheet that's given to us on tests so we won't need to memorize the conversion

Rosha Mamita 2H

when there are an increased number of oscillations in a certain amount of time (frequency), the distance between the peaks (wavelength) decrease, and vise versa

Rosha Mamita 2H

I think it would be better to remember the main ones just in case such as UV light, infrared light, and visible light, and even then just a general idea of where on the spectrum the light is in terms of numbers. Otherwise I'm not sure what information about the light spectrum will be provided on our...

Rosha Mamita 2H

The answers will probably be in some form of meters, but unless the units are specified I don't think it will matter what kind of unit in meters you use. Being consistent with units is always a better choice though.

Rosha Mamita 2H

Amplitude and frequency are related in that they are inversely proportional to one another. So, if the amplitude increases, the frequency decreases, or if the amplitude decreases, the frequency increases. This relationship is derived from the equation v = c/(lamda). I believe its the frequency and ...

Rosha Mamita 2H

using sig figs during your calculations wont necessarily get you a wrong answer, just maybe a slightly less accurate answer. I believe you should just use sig figs at the end of your answer though, that's what I learned in AP Chem. It's especially helpful for when there aren't many sig figs in the q...

Rosha Mamita 2H

I believe we dont need to round up the atomic masses in the periodic table, the reason being it would make our calculated answers for problems slightly less accurate than the real answers

Rosha Mamita 2H

yep, you'd multiply your resulting moles for part b with the molar mass of both the CuSO4 combined with the 5H20, which would be a combined molar mass of 324.65g/mol.

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